Magpie converts pubDates to unix timetamps, stored in each item as $item[‘date_timestamp’]. So in your script this line:
$item_new->date = $item[‘pubdate’];

…should change to:
$item_new->date = $item[‘date_timestamp’];

Secondly, the copy of feedcreator.class.php has a little bug. The FeedDate object’s rfc822() method uses time() instead of the stored unix date. So $date within that function should be set like this instead:
$date = gmdate(“D, d M Y H:i:s”, $this->unix);